Charles l



(No Model.)

0. L. DAVIS. INSTRUMENT FOR DRAWING GEOMETRIGAL CURVES.

No. 486,699.. Patented Nov. 22., 1892..

INVENTOH WITNESSES ATTORNEYS.

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' head 0 of the leg A.

" "UNITED STATES PATENT OFFICE.

CHARLES L. DAVIS, OF NEXV YORK, N. Y.

INSTRUMENT FOR DRAWING GEOMETRICAL CURVES.

SPECIFICATION forming part of Letters Patent No. 486,699, dated November22, 1892.

Application filed April 19, 1892.

To all whom it may concern.-

Be it known that I, CHARLES L. DAVIS, of the city, county, and State ofNew York, have invented a new and improved Draftsmans Compass, of whichthe following is'a full, clear, and exact description.

The invention relates to drawing-instruments; and its object is toprovide a new and improved draftsmans compass which is simple anddurable in construction and more especially designed for convenientlyand rapidly drawing spiral lines, ovals, ellipses, and other curvilineargeometrical lines and figures.

The invention consists principally of a cord connected with one of thelegs of the compass and adapted to wind on a drum mounted to rotateloosely on the spindle held on the other leg at the joint of both legs.

The invention also consists of certain parts and details andcombinations of the same, as Willbe hereinafter described,and thenpointed out in the claims.

Reference is to be had to the accompanying drawings, forming a part ofthis specification, in which similar letters of reference indicatecorresponding parts in both the figures.

Figure 1 is a perspective View of the improvement. Fig. 2 is a plan Viewof a modified form of the improvement.

The compass is provided with the legs A and B, of which the leg B ispivoted in the The leg A is provided with the usual point D and theother leg B carries a pen, pencil,or other device for drawing thedesired line. On the leg B, preferably on the joint E, is j ourn aled aroller F, to which is attached one end of a cord or thread G, extendingunder a pulley H, journaled on the other leg A. The cord or thread thenextends upward and passes over a pulley I, journaled in the outer end ofa rod I, attached to and projecting from the head 0 of the leg A. v

The cord or thread G then passes to a sleeve J, on which it may befastened or adapted to be wound thereon, as hereinafter more fullyexplained. The sleeve or drum J is mounted to turn on a pin K, extendingupwardly from the head 0, and on the upper end of this pin is fastened aknob or handle L for conveniently turning the instrument so that the legB moves around the leg A, as hereinafter more fully described.

From the drum or ward the leg A.

Serial No. 429,709. (No model.)

sleeve J extends outwardly a rod N, carrying a ring 0, adapted to beengaged by one of tho fingers of the operators hand when using theinstrument. On the sleeve or drum J is also secured a bar P, extendingto both sides of the sleeve and on which is adapted to wind the cord orthread G for the purpose presently to be described. A spring Q isattached with one end to the head 0 and presses with its free end on theleg B, so as to return the same to an outermost position and to hold thesaid leg in proper position while drawing the desired line.

The instrument is used as follows: For drawing spirallines the upper endof the cord or thread G is preferably attached to the bar P and thenwound several times around the sleeve or drum J, after which it isextended to the pulleys I, H, and F, as shown and described. The point Dof the leg A is then placed on the desired center of the line to bedrawn and the leg B is extended outwardly to the outer end of the lineto be drawn. The operator takes hold with his thumb and forefinger andplaces the little finger into the ring 0. By now turning the knob Lwithout changing the position of the hand the leg B revolves around theleg A, the point of which is held in the center in the usual way. Now itwill be seen that as the leg Arev'olves with the point D remaining inthe center the arm I, carrying the pulley I, moves with it, and as thedrum J is held stationary by the fingerriug O and rod N the cord orthread winds up on the drum or sleeve J and in doing so draws the leg Binwardly, the latter swinging from the joint in the headC toward theother leg A. As this operation is continued the leg B is gradually drawnin toward the other leg A, and consequently the distance between the twolegs becomes gradually less, so that a spiral will be drawn. It will beseen that the leg B is always held sufficiently taut to prevent the saidlegs from closing too rapidly to- \Vhen it is desired to draw ovals,ellipses, and other curvilinear geometrical lines and figures, then adisk R (see Fig. 2) of corresponding form is used in the place of thearm P and a double thread T is attached to the arm 1 arranged oppositethe arm I, and the two parts of the thread T are passed over theperiphery of the disk R to be attached to the thread G at or' near thepulley I. Now when the device is used in the manner above described thecord or thread G is drawn in or let out, according asthe double threadis acted on by the disk. In doing this it is understood that the leg Bis drawn toward the leg A, when a pull is exerted on the cord or threadG at the time the widest part of the disk R moves away from the pulley Iand until this widest part stands at right angles to the arms I and 1but when in the course of rotating the handle L the widest part movestoward the end of arm 1 or toward the, pulley I, then the cord becomesslack; but this is taken up at once by the action of the spring Q on theleg B, which is forced correspondingly outward. In this manner ovals,ellipses, and other figures can be drawn, it being understood, however,that for drawing such figures difi'erent lengths and forms of disks areused instead of the bar P.

It is further understood that in drawing spiral lines, as abovedescribed, the form of the spiral-that is, the distance between twoadjacent linesisregnlated by using sleeves or drums J ofdifferentdiameters, so that the winding up of the cord orthread G ismore or less for each revolution made by the instrument.

Having thus fully described my invention, I claim as new and desire tosecure by Letters Patent- 1. In a drawing-instrument, the combination,with a compass, of a cord connected with one of the legs of the compassand a drum or sleeve mounted to rotate loosely on the spindle or pinheld on the head of the compass, the said drum being adapted to wind upthe said cord, substantially as shown and described.

2. In a drawing-instrument, the combination, with a eompass,of a cordconnected with one of the legs of the compass, a drum or sleeve mountedto rotate loosely on the spindle or pin held on the head of the compass,the said drum being adapted to wind up the said cord, and a device forholding the said drum stationary while the compass is turned,substantially as shown and described.

3. A draftsmans compass provided with a drum or sleeve mounted looselyon a spindle projecting from the head of the compass, a rod extendingfrom the said drum and provided with a finger-ring for holding the saiddrum stationary while the compass is turned, and a cord connected withthe said drum and with one of the legs of the compass, substan tially asshown and described.

4. A draftsmans compass provided with a drum or sleeve mounted looselyon a spindle projecting from the head of the compass,a

rod extending from the said drum and provided with a finger-ring forholding the said drum stationary while the compass is turned, a cordconnected with the said drum and with one of the legs of the compass,and a bar projecting from the said drum, substantially as shown anddescribed.

5. A draftsmans compass provided with a drum or sleeve mounted looselyon a spindle projecting from the head of the compass, a rod extendingfrom the said drum and provided with a finger-ring for holding the saiddrum stationary while the compass is turned, a cord connected with thesaid drum and with one of the legs of a compass, a bar projecting fromthe said drum, and a spring pressing on the said leg, to which the cordis fastened, substantially as shown and described.

6. In a drawing-instrument, the combination, with a compass provided onits head with a spindle or pin carrying a knob or handle, of a sleeveheld loosely on the said spindle and provided with a finger-ring forholding the drum stationary while the compass is turned, and a cord orthread connected at one end with the said drum and passing over pulleysheld on one of the legs to engage and connect with the other leg of thecompass, substantially as shown and described.

7. In a drawing-instrument, the combination, with a compass provided onits head with a spindle or pin carrying a knob or handle, of a sleeveheld loosely on the said spindle and provided with a finger-ring forholding the drum stationary while the compass is turned, a cord orthread connected at one end with the said drum and passing over pulleysheld on one of the legs to engage and connect with the other leg of thecompass, and a bar held on the said drum and adapted to engage the cordor thread, substantially as shown and described.

8. In a drawing-instrument, the combination, with a compass provided onits head with a spindle or pin carryinga knob or handle, of a sleeveheld loosely on the said spindle and provided with a finger-ring forholding the drum stationary while the compass is turned, a cord orthread connected at one end with the said drum and passing over pulleysheld on one of the legs to engage and connect with the other leg of thecompass, a bar held on the said drum and adapted to engage the cord orthread, and a spring pressing one of the said legs outward,substantially as shown and described.

CHARLES L. DAVIS.

Witnesses:

J. G. MCCABE, A. JOSEPH.

